Excessive cola consumption can lead to anything from mild weakness to profound muscle paralysis, doctors are warning.

This is because the drink can cause blood potassium to drop dangerously low, they report in the International Journal of Clinical Practice.

They tell of the curious case of an Australian ostrich farmer who needed emergency care for lung paralysis after drinking 4-10 litres of cola a day.

He made a full recovery and was advised to curtail his cola drinking.

Another example included a pregnant woman who regularly consumed up to three litres a day for the last six years and complained of tiredness, appetite loss and persistent vomiting.

A heart trace revealed she had an irregular heartbeat, most likely caused by her low blood potassium levels.

Once she stopped drinking so much cola, she made a full and uneventful recovery.

The investigators believe these cases are not atypical and that many people risk problems due to their intake.

Manufacturers insist the products are safe when consumed in moderation.

In a commentary, Dr Clifford Packer from the Louis Stokes Cleveland VA Medical Centre in Ohio said: "We have every reason to think that it is not rare.

"With aggressive mass marketing, super-sizing of soft drinks, and the effects of caffeine tolerance and dependence, there is very little doubt that tens of millions of people in industrialised countries drink at least 2-3 l of cola per day.

"It follows that the serum potassium levels of these heavy cola drinkers are dropping, in some cases, to dangerous low levels."